#include <iostream>
#include <GL/glut.h>
#include <cstdio>
#include <cstdlib>
#include <cmath>

void init(){
    glClearColor(1.0, 1.0, 1.0, 0.0);   //Set display-window color to white.
    glMatrixMode(GL_PROJECTION);        //Set projection parameters.
    gluOrtho2D(0.0, 200.0, 0.0, 150.0);
}
void lineSegment(){
    glClear(GL_COLOR_BUFFER_BIT);   //Clear display window.

    glColor3f(1.0, 0.0, 0.0);       //Set line segment color to red.
    glBegin(GL_LINES);
    glVertex2i(180, 45);        //Specify line-segment geometry
    glVertex2i(10, 145);
    glEnd();

    glFlush();      //Process all OpenGL routines as quickly as possible.
}

int main(int argc, char **argv) {
    glutInit(&argc, argv);                          //Initialize GLUT.
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);    //Set display mode.
    glutInitWindowPosition(50, 100);    //Set top-left display-window position.
    glutInitWindowSize(400, 300);       //Set display-window width and height.
    glutCreateWindow("An example OpenGL Program");  //Create display window.

    init();                         //Execute initialization procedure.
    glutDisplayFunc(lineSegment);   //Send graphics to display window.
    glutMainLoop();                 //Display everything and wait.
    return 0;
}